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2-Azetidinones s. a. Penicillin

In addition to the S—C-2 bond cleavages described thus far, both S—C-5 and C-3—N bond cleavage have been explored in penicillin degradation. Chlorinolysis of penicillin effects S—C-5 cleavage, affording the 4-chloro-2-azetidinone (105 t,y), from which the cephalosporin disulphide (106 f,z) was prepared (Scheme 4). The structure and stereochemistry of (106) were determined by X-ray techniques. Chlorinolysis of an N-trityl-anhydropeni-cillintoluene-p-sulphonate (107 g) gave, after hydrolysis, a sulphur-free 2-azetidinone (108 z, R = NHi), which cyclized to the oxazoline (109) on reaction with chloroformate esters. Allylic bromination of (108 f, y) afforded a monobromide (110), from which the azacephem (111 f, y) was obtained by... [Pg.206]

Thiazoline-azetidinone 36 is a versatile intermediate for the synthesis of varieties of beta-lactam antibiotics 24>. The most straightforward route to 36 must be the removal of the feta-lactam A-substituents of thiazoline-azetidinone 35, which is readily obtained from penicillins by Copper s method 4>. This has usually been done by the two-step operation, involving ozonolysis and subsequent methanolysis 25). Direct transformation of 35 to 36 also has been achieved by oxidation with potassium permanganate or osminum tetraoxide, but yields are unsatisfactory (—37%)25). An efficient method for the removal of A-substituents of 35 is the electrochemical acetoxylation procedure which may lead to the compound 36 along with 37 (Scheme 2-12)3). For example, the... [Pg.164]

To determine which carbon atom of the isopropenyl functionality in the azetidinone sulfinyl chloride participates in the ring closure, the above sequence of steps was repeated starting with the penicillin sulfoxide ester deuterated at the C-2 methyl position. The stereochemistry of this compound (70) had been previously established (Cooper, 1970). The NMR spectrum of the final product, methyl phthalimido-2-dideutero-3-methy-lenecepham-4-carboxylate (71), showed clearly a selective incorporation of deuterium at the C-2 position. It was, therefore, concluded that the olefinic carbon in the intermediary sulfinyl chloride was involved in the S—C-2 bond formation. [Pg.108]


See other pages where 2-Azetidinones s. a. Penicillin is mentioned: [Pg.258]    [Pg.249]    [Pg.221]    [Pg.237]    [Pg.244]    [Pg.258]    [Pg.249]    [Pg.221]    [Pg.237]    [Pg.244]    [Pg.797]    [Pg.111]    [Pg.209]    [Pg.100]    [Pg.184]    [Pg.199]    [Pg.56]    [Pg.351]    [Pg.194]    [Pg.194]    [Pg.1979]    [Pg.97]    [Pg.8]   


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2-Azetidinone

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